In anticipation for Yahoo! and TRI Studio's live stream of Lukas Nelson & Promise of the Real tonight at 7pm PT / 10pm ET, we've got exclusive rehearsal clips of the Willie Nelson progeny and his band hanging out with none other than the venerable Bob Weir of the Grateful Dead (not to mention a special bonus video at the end)! Watch the up-and-coming rock musician and the legendary artist jam and chat about Buddy Holly and Jerry Garcia while you get stoked for tonight's live stream!